1. Field of the Invention
The present invention relates to a starter for cranking an internal combustion engine, the starter having a one-way clutch spline-coupled to an output shaft.
2. Description of Related Art
An example of a starter having a one-way clutch spline-coupled to an output shaft is disclosed in JP-A-2005-120899. The one-way clutch is composed of a clutch-outer driven by an electric motor and a clutch-inner coupled to the clutch-outer via clutch rollers. The tube-shaped clutch inner has a female spline that is connected to a male spline formed on the output shaft. A rotational torque of the electric motor is transmitted to the output shaft via the one-way clutch.
In this starter, air in a space behind a rear end of the output shaft is compressed or expanded according to reciprocal movement of the output shaft in the axial direction. In other words, the air in the space is subjected to a pumping action of the reciprocating output shaft. Lubricant such as grease retained in a space between the clutch-inner and the output shaft moves out to the space behind the read end of the output shaft according to the pumping action of the output shaft. This results in shortage of the lubricant between the output shaft and the clutch-inner.
In addition, it is possible that the lubricant entered the space behind the output shaft flows out into a further rear side space. The space behind the output shaft may be closed to prevent the lubricant flow. However, it cannot be avoided that the air in the space behind the output shaft is subjected to a pumping action of the reciprocating output shaft. According to the pumping action, pressure in the space changes and lubricant may be scattered around.